There are a number of benefits but one of the most important reasons is that the spam filtering system on our new mailserver is much simpler to use than the current old one. You simply drag or move messages in and out of a special “Spam” folder to retrain the spam filter for your mailbox. This is an important security issue that helps prevent both email users and the mailserver system from serious phishing attacks, and reduces general spam by up to 99% once the spam filter is trained properly for your particular incoming email.
IMAP stores messages on the remote mailserver and is specifically designed to allow connections from multiple devices. Using mobile phones and separate home and office computers via IMAP means email can be reliably accessed from anywhere because all messages on all devices are synchronized. The status of a viewed or deleted message will be reflected on all devices. You can also create multiple folders to help organise your messages and these folders are also available on all devices.
From a Spiderweb perspective, in the “old days” it was easier to set up a POP account because IMAP was new and still being developed. Then we introduced the first versions of our spam filter which requires access to special folders so a lot of users would then hop over to our webmail system to train their spam filter then go back to using POP from their normal mail program. These days using webmail just for spam training is unnecessary if your mailbox access method is changed to IMAP. Then you can easily train your spam filter from within the same program you use to check your email.